import java.util.ArrayList;
import java.util.List;

public class BinaryTree {
    static class TreeNode{
        public char val;
        public TreeNode left;
        public TreeNode right;

        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode createTree(){
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        return A;//返回头节点
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null) return;
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    //遍历思路：我遍历到根放到list里面
    List<Character> list = new ArrayList<>();
    public List<Character> preorderTraversal(TreeNode root) {
        if(root == null) return list;
        list.add(root.val);
        preorderTraversal(root.left);
        preorderTraversal(root.right);
        return list;
    }

    //子问题：根放进来
    public List<Character> preorderTraversal2(TreeNode root){
        List<Character> list = new ArrayList<>();
        if(root == null) return list;
        list.add(root.val);

        List<Character> leftTree = preorderTraversal2(root.left);
        list.addAll(leftTree);

        List<Character> rightTree = preorderTraversal2(root.right);
        list.addAll(rightTree);

        return list;
    }
    // 中序遍历
    public void inOrder(TreeNode root) {
        if(root == null) return;
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }
    // 后序遍历
    public void postOrder(TreeNode root) {
        if(root == null) return;
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    // 获取树中节点的个数
    public static int nodeSize = 0;
    public void size(TreeNode root){
        if(root == null){
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    public int size2(TreeNode root){
        if(root == null){
            return 0;
        }
        return size2(root.left)+size2(root.right)+1;
    }

    // 获取叶子节点的个数
    public static int leafSize = 0;
    public void getLeafNodeCount(TreeNode root){
        if(root == null){
            return;
        }
        if(root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount(root.left);
        getLeafNodeCount(root.right);
    }

    public int getLeafNodeCount2(TreeNode root){
        if(root == null){
            return 0;
        }
        if (root.left == null && root.right == null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    //获取第K层节点的个数
    public int getKLevelNodeCount(TreeNode root,int k){
        if(root == null){
            return 0;
        }
        if(k == 1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    }

    public int getHeight(TreeNode root){
        if(root == null){
            return 0;
        }
        int leftHeight = getHeight(root.left);
        int rightHeight = getHeight(root.right);
        return Math.max(leftHeight,rightHeight)+1;
    }

    // 检测值为value的元素是否存在
    public TreeNode find(TreeNode root, int val){
        if(root == null){
            return null;
        }
        if(root.val == val){
            return root;
        }
        TreeNode leftT = find(root.left,val);
        if(leftT != null){
            return leftT;
        }
       TreeNode rightT = find(root.right,val);
        if(rightT != null){
            return rightT;
        }
        return null;
    }
}
